The present invention relates to a clamp device drive apparatus for driving a clamp device for clamping an object (workpiece or tool etc.) to be clamped on a base member of a press machine or machining machine.
In the industrial field, the clamp device drive apparatus is known and applied in order to drive the clamp device between a clamping position for clamping the object such as a die and workpiece, and an unclamping position away from the object along a T-shaped groove formed horizontally on a surface of the base member of the machine.
Generally, the clamp device drive apparatus comprises a push-pull chain connected to the clamp device at its one end and capable of pushing and pulling it along the T-shaped groove, a sprocket engaged with the push-pull chain and supported rotatably with a shaft, and a drive motor for rotating the sprocket.
In the prior clamp device drive apparatus, two types of the drive motors for rotating the sprocket, one employing an electric motor with reduction gears, the other employing a hydraulic or pneumatic motor, are applied.
With regard to several defects of these prior drive motors, the former is rather large in size, therefore it can not be mounted in a limited space around the machine, and the reduction gears are expensive in manufacturing cost, its drive torque can not be easily changed corresponding to the weight and size of the clamp device, the latter is not free from such defects that its torque is small and its rotation can not be stabilized in low rotating speed, especially in starting.
In order to generate high torque in low rotating speed, the motor should include reduction gears, but reduction gears can not be recommended because of high cost.
Accordingly, it is possible to apply various cylinder drive type motors employing pressurized fluid, which are relatively small in size and capable of generating high torque in low rotating speed.
For examples, in Japanese Patent Laid-open Publication No. 54-120, 338 or Japanese Patent Laid-open Publication No. 60-56, 101 proposed by the applicant of the present invention, cylinder drive type motors with a rack-pinion mechanism for converting a driving force of a pneumatic cylinder into rotating torque are disclosed. In Japanese Patent Application No. 2-151, 262, the applicant of the present invention proposed a cylinder drive type motor with a crank mechanism for converting the driving force of a pneumatic cylinder into rotating torque.
However, in these cylinder drive type motors with the rack-pinion or crank mechanism, it is necessary to provide a long rack member or connecting rod member on the piston rod of the pneumatic cylinder. Therefore, it is impossible to miniaturize the motor size and to decrease the number of necessary parts for the rack-pinion or crank mechanism and to save the manufacturing cost.